Redispatching active and reactive powers using a limited number of control actions

This paper deals with some essential open questions in the field of
optimal power flow (OPF) computations, namely: the limitation of
the number of controls allowed to move, the trade-off between the
objective function and the number of controls allowed to move,
the computation of the minimum number of control actions needed to
satisfy constraints, and the determination of the sequence
of control actions to be taken by the system operator in order to
achieve its operation goal.
To address these questions, we propose approaches which rely on
the computation of sensitivities of the objective function and
inequality constraints with respect to control actions. We thus
determine a subset of controls allowed to move in the OPF, by solving
a sensitivity-based mixed integer linear programming (MILP) problem.
We study the performances of these approaches on three test systems
(of 60, 118, and 618 buses) and by considering three different OPF
problems important for a system operator in emergency and/or in
normal states, namely the removal of thermal congestions, the
removal of bus voltage limits violation, and the reduction of
the active power losses.